Film forming apparatus, film forming method, and recording medium

ABSTRACT

A film forming apparatus includes a rotary table having a loading area at a first surface side thereof and revolving a substrate loaded on the loading area, a rotation mechanism rotating the loading area such that the substrate rotates around its axis, a processing gas supply mechanism supplying a processing gas to a processing gas supply area so that a thin film is formed on the substrate which repeatedly passes through the processing gas supply area the revolution of the substrate, and a control part configured to perform a calculation of a rotation speed of the substrate based on a parameter including a rotation speed of the rotary table to allow an orientation of the substrate to be changed whenever the substrate is positioned in the processing gas supply area, and to output a control signal for rotating the substrate at a calculated rotation speed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2014-223701, filed on Oct. 31, 2014, in the Japan Patent Office, thedisclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to a film forming apparatus and a filmforming method of forming a thin film by supplying a processing gas tothe substrate, and a recording medium.

BACKGROUND

A film forming apparatus which performs an atomic layer deposition (ALD)method as a method of forming a thin film of silicon oxide (SiO₂) or thelike on a substrate such as semiconductor wafer (hereinafter, referredto as “wafer”) has been known. As an example of this type film formingapparatus, there is an apparatus which includes a processing chamberwhose inside can be kept in a vacuum atmosphere and a rotary tablemounting thereon a wafer and installed in the processing chamber. A gasnozzle for discharging a source gas that is a raw material for thesilicon oxide or the like and a gas nozzle for discharging an oxidizinggas for oxidizing the source gas are arranged above the rotary table. Asilicon oxide film is formed on a wafer in such a way that the waferrepeatedly and alternately passes through an adsorption area where thesource gas is supplied and an oxidation area where the oxidizing gas issupplied, while revolving by the rotation of the rotary table.

In order to control the distribution of in-plane film thickness of thewafer in the ALD method, a distribution of the source gas adsorbed onthe wafer needs to be controlled, and hence the number and locations ofejection holes of the gas nozzle for discharging the source gas areappropriately adjusted in the film forming apparatus. In addition,selecting a shape of the gas nozzle, an adjustment of a supply amount ofa separation gas which is supplied to compart the adsorption area andthe oxidation area, and an adjustment of a concentration of a carriergas in the source gas are properly performed.

On the other hand, there is sometimes the case where an etching rate canbe adjusted for each of a peripheral area and a center area of the waferin an etching process performed on the wafer after the film formingprocess. In this case, since a uniform film thickness can be obtained onthe circumferential area and the center area after the etching, auniform film thickness needs to be obtained particularly along thecircumferential direction of the wafer. However, due to theabove-mentioned revolution of the wafer, each portion of the waferrepeatedly travels the same orbit that is separated from a rotationcenter of the rotary table by a predetermined distance. Accordingly,there is a possibility that a fluctuation of the distribution of thesource gas in the adsorption area leads to a fluctuation of the filmthickness on the wafer in a radial direction of the rotary table, andthat this fluctuation of the film thickness can not be sufficientlycontrolled by the adjustment of the number and locations of the ejectionholes or the like.

In a conventional film forming apparatus in which the wafer revolves, inorder to improve the uniformity of the film thickness in thecircumferential direction of the wafer, a mechanism is provided forchanging an orientation of the wafer by lifting the wafer placed on therotary table from the rotary table when the rotary table is stopped in apredetermined orientation and then placing the wafer on the rotary tableagain. However, in this type of film forming apparatus, the throughputmay decrease because the rotary table is stopped for every change of theorientation of the wafer.

In another conventional film forming apparatuses in which the waferrevolves, a wafer loaded on a rotary table rotates on its axis while therotary table rotates. However, the film forming apparatus does notparticularly provide the number of rotations set for wafer rotation.When the number of rotations of the wafer is not appropriately set, thewafer rotation and the wafer revolution may be synchronized with eachother. That is, when the wafer rotation and the wafer revolution aresynchronized with each other, the wafer may pass through the adsorptionarea in the same orientation, thereby leading to an insufficientuniformity of the film thickness on the wafer in the circumferentialdirection.

SUMMARY

Some embodiments of the present disclosure provide a technology forimproving the in-plane uniformity of film thickness in thecircumferential direction on a substrate when performing a film formingprocess on a substrate loaded on a rotary table by revolving thesubstrate.

According to the present disclosure, there is provided a film formingapparatus of forming a thin film on a substrate by supplying aprocessing gas to the substrate, the film forming apparatus including: arotary table disposed in a vacuum chamber and having a loading areaformed at a first surface side of the rotary table, the rotary tableconfigured to revolve the substrate loaded on the loading area; arotation mechanism configured to rotate the loading area such that thesubstrate rotates around its axis; a processing gas supply mechanismconfigured to supply the processing gas to a processing gas supply areaat the first surface side of the rotary table so that the thin film isformed on the substrate which repeatedly passes through the processinggas supply area for a plurality of times by the revolution of thesubstrate; and a control part configured to perform a calculation of arotation speed of the substrate based on a parameter including arotation speed of the rotary table to allow an orientation of thesubstrate to be changed whenever the substrate is positioned in theprocessing gas supply area, and to output a control signal for rotatingthe substrate at a calculated rotation speed.

According to the present disclosure, there is provided a method offorming a thin film on a substrate by supplying a processing gas to thesubstrate, the method including: loading the substrate on a loading areaformed at a first surface side of a rotary table disposed in a vacuumchamber and revolving the substrate; rotating the loading area by arotation mechanism to rotate the substrate; supplying the processing gasto a processing gas supply area at the first surface side of the rotarytable by a processing gas supply mechanism so that the thin film isformed on the substrate which repeatedly passes through the processinggas supply area by a plurality of times; calculating a rotation speed ofthe substrate based on a parameter including a rotation speed of therotary table to allow an orientation of the substrate to be changedwhenever the substrate is positioned in the processing gas supply area,and rotating the substrate at a calculated rotation speed.

According to the present disclosure, there is provided a non-transitorycomputer-readable recording medium storing therein a computer programused in a film forming apparatus in which a thin film is formed on asubstrate by supplying a processing gas to the substrate, wherein thecomputer program is configured to execute the above method.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentdisclosure, and together with the general description given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present disclosure.

FIG. 1 is a longitudinal cross-sectional view of a film formingapparatus according to the present disclosure.

FIG. 2 is a plan view of the film forming apparatus shown in FIG. 1.

FIG. 3 is a perspective view of an inside of the film forming apparatusshown in FIG. 1.

FIG. 4 is a perspective view of an upper-side rotary table of the filmforming apparatus shown in FIG. 1.

FIG. 5 is a perspective view of a lower-side of the rotary table.

FIG. 6 is a block diagram of a control part of the film formingapparatus shown in FIG. 1.

FIGS. 7 to 10 are explanatory diagrams for illustrating position andorientation of a wafer during a film forming process.

FIG. 11 is an explanatory diagram for illustrating flow of a gas overthe rotary table during a film forming process.

FIG. 12 is a longitudinal cross-sectional view of an example of a waferholder installed in the rotary table.

FIG. 13 is a longitudinal cross-sectional view of an example of a vacuumchamber of the film forming apparatus.

FIG. 14 is a longitudinal cross-sectional view of a film formingapparatus according to another embodiment of the present disclosure.

FIG. 15 is a perspective view of an upper-side of a rotary table of thefilm forming apparatus shown in FIG. 14.

FIGS. 16 to 18 are schematic diagrams for illustrating a rotation of awafer loaded on the rotary table.

FIG. 19 is a perspective view of an upper-side of a rotary table ofanother film forming apparatus.

FIGS. 20A and 20B and 21A and 21B are schematic diagrams forillustrating a distribution of film thickness on a wafer obtained fromevaluation tests.

FIGS. 22A and 22B and 23A and 23B are graphs showing a distribution offilm thickness on a wafer obtained from evaluation tests.

FIGS. 24A and 24B and 25A and 25B are schematic diagrams forillustrating a distribution of film thickness on a wafer obtained fromevaluation tests.

FIGS. 26A and 26B and 27A and 27B are graphs showing a distribution offilm thickness on a wafer obtained from evaluation tests.

FIGS. 28A to 28C and 29A to 29C are schematic diagrams for illustratinga distribution of film thickness on a wafer obtained from an evaluationtest.

FIGS. 30A and 30B are graphs showing a distribution of film thickness ona wafer obtained from evaluation tests.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present disclosure. However,it will be apparent to one of ordinary skill in the art that the presentdisclosure may be practiced without these specific details. In otherinstances, well-known methods, procedures, systems, and components havenot been described in detail so as not to unnecessarily obscure aspectsof the various embodiments.

A film forming apparatus 1 for performing an ALD on a substrate such asa wafer is described below. The apparatus 1 is an example of a vacuumprocessing apparatus according to the present disclosure. In the filmforming apparatus 1, BTBAS (Bis(tertiary-butyl-amino) silane) gas as asource gas that is a processing gas including Si (silicon) is adsorbedon a wafer W, a molecular layer of SiO₂ (silicon oxide) is formed bysupplying an ozone (O₃) gas as an oxidizing gas for oxidizing theadsorbed BTBAS gas, and the molecular layer is exposed to a plasmagenerated from a gas for generating the plasma. This series of processesis repeatedly performed by a plurality of times to form a SiO₂ film onthe wafer W.

FIGS. 1 and 2 are a longitudinal cross-sectional view and a plan view ofthe film forming apparatus 1, respectively. The film forming apparatus 1includes a vacuum chamber (processing chamber) 11 that is substantiallycircular and flat in shape, and a rotary table (susceptor) 2 havingcircular disk-shape and horizontally disposed in the vacuum chamber 11.The vacuum chamber 11 includes a ceiling plate 12 and a chamber body 13that defines a side wall and a bottom portion of the vacuum chamber 11.

A center shaft 21 is installed extending from the center portion of therotary table 2 in a vertical downward direction. The center shaft 21 iscoupled to a rotation driving part 22 provided to block an openingportion 14 formed on the bottom portion of the chamber body 13. Therotary table 2 is supported by the center shaft 21 and the rotationdriving part 22 in the vacuum chamber 11, and rotates in a clockwisedirection when seen in a plan view. A gas supply pipe 15 shown in FIG. 1discharges an N₂ (nitrogen) gas into a gap between the center shaft 21and the chamber body 13, and serves to prevent the source gas andoxidizing gas from being introduced to a rear surface of the rotarytable 2 from a front surface of the rotary table 2 by discharging the N₂gas in processing the wafer W.

Further, a center area forming portion C protruding to face the centerportion of the rotary table 2 and having a circular shape when seen in aplan view, and protrusions 17 each having a fan shape when seen in aplan view such that the protrusion 17 are formed to have a more widenedwidth along a direction from the center area forming portion C toward aradially outward position of the rotary table 2 are formed on a bottomsurface of the ceiling plate 12 of the vacuum chamber 11. That is, thecenter area forming portion C and the protrusions 17 constitute a lowerceiling surface compared with other areas. A gap between the center areaforming portion C and the center portion of the rotary table 2 forms aflow path 18 for the N₂ gas. The N₂ gas is supplied to the flow path 18from a gas supply pipe coupled to the ceiling plate 12 when processingthe wafer W, and then discharged toward the entire outer circumferenceof the rotary table 2 from the flow path 18. The N₂ gas prevents thesource gas and the oxidizing gas from being mixed with each other overthe center portion of the rotary table 2.

FIG. 3 is a perspective view of a bottom of an inside of the chamberbody 13. A concave portion 31 having a flat ring shape is formed on thechamber body 13 on the lower side of the rotary table 2 along thecircumference of the rotary table 2. A slit 32 having a ring shape isopened on a bottom surface of the concave portion 31 along acircumferential direction of the concave portion 31. The slit 32 isformed to penetrate through the bottom portion of the chamber body 13 ina thickness direction. A heater 33 for heating the wafer W loaded on therotary table 2 is arranged in a form of seven rings on a bottom surfaceof the concave portion 31. In FIG. 3, the heater 33 is shown by cuttingaway some portions thereof for the sake of simplicity.

The heater 33 is arranged along concentric circles centered at arotation center of the rotary table 2, and among the seven heaters 33,four heaters are arranged on the inner side of the slit 32 and threeheaters are arranged on the outer side of the slit 32. Further, a shield34 is provided to cover an upper side of each heater 33 and to shield anupper side of the concave portion 31 (see FIG. 1). The shield 34includes a slit 37 having a ring shape aligned with the slit 32, and arotation shaft 26 and a strut 41, which will be described later,penetrate through the slit 37. Evacuation ports 35 and 36 for evacuatingthe vacuum chamber 11 are provided on an outer side of the concaveportion 31 at the bottom portion of the chamber body 13. An evacuationmechanism (not shown) including a vacuum pump or the like is coupled tothe evacuation ports 35 and 36.

The rotary table 2 is further described with reference to FIGS. 4 and 5respectively illustrating an upper side and a lower side thereof. Fivecircular concave portions are formed along a rotational direction of therotary table 2 on the frontal surface side (one surface side) of therotary table 2, and a circular wafer holder 24 is provided on each ofthe concave portions. A recess portion 25 is formed on a frontal surfaceof the wafer holder 24, and the wafer W is horizontally placed on therecess portion 25. Accordingly, the bottom of the recess portion 25defines a loading area where the wafer is loaded. In this example, aheight of a side wall of the recess portion 25 is similar to a thicknessof the wafer W, e.g., 1 millimeter.

For example, three struts 41 extend in a vertically downward directionfrom locations separate from each other in a circumferential directionof the rear surface of the rotary table 2, and as shown in FIG. 1, alower portion of each of the struts 41 penetrates the bottom portion ofthe chamber body 13 through the slit 32 and is coupled to a support ring42 that is a coupling part arranged on the lower side of the chamberbody 13. The support ring 42 is formed along the rotational direction ofthe rotary table 2, while being horizontally arranged and suspended fromthe chamber body 13 by the strut 41. The support ring 42 rotates withthe rotary table 2.

The rotation shaft 26 that serves as a rotational axis extends in avertically downward direction from the lower-side center portion of thewafer holder 24. A lower portion of the rotation shaft 26 penetrates therotary table 2, penetrates the bottom portion of the chamber body 13through the slit 32, as shown in FIG. 1, further penetrates the supportring 42 and a magnetic sealing part 20 provided on the lower side of thesupport ring 42, and coupled to a rotation driving part 27 for waferrotation. The magnetic sealing part 20 includes a bearing for rotatablysupporting the rotation shaft 26 against the support ring 42 and amagnetic seal (magnetic fluid seal) sealing a gap around the rotationshaft 26.

The magnetic seal is provided such that a particle originating from thebearing, e.g., a lubricant used for the bearing is suppressed from beingspread to a vacuum atmosphere outside the magnetic sealing part 20. Bysupporting the rotation shaft 26 with the bearing, the wafer holder 24is slightly upwardly separated from, e.g., the rotary table 2. Therotation driving part 27 for the wafer rotation includes a motor and isdisposed in the lower side of the support ring 42 via the magneticsealing part 20 to rotate the rotation shaft 26 about an axis thereofusing the motor. When the rotation shaft 26 is rotated and supported inthis manner, the wafer holder 24 rotates in a counterclockwise directionwhen seen, for example, in a plan view.

The wafer W rotates (wafer revolution) around the center shaft of therotary table 2 due to the rotation of the rotary table 2, and the waferW rotates around the center of the wafer W due to the rotation of thewafer holder 24. The rotation of the wafer W around the center of thewafer W may be referred to as a rotation of a wafer. In the film formingapparatus 1, the revolution and the rotation of the wafer W areperformed in parallel when forming a thin film on the wafer W. Therotation of the wafer W includes an intermittent rotation around thecenter of the wafer W, as well as a continuous rotation around thecenter of the wafer W. In the case of the intermittent rotation, therotation of the wafer W includes a case where the rotation of the waferW is stopped before completing one rotation or more around the center ofthe wafer W and then the rotation is resumed.

A shield ring 44 is disposed so as to be overlapped with the supportring 42, and in FIGS. 4 and 5, the shield ring 44 is shown in a dottedand dashed line for the sake of brevity. As shown in FIG. 1, the shieldring 44 is provided to block the slit 32 of the chamber body 13 from thelower side of the chamber body 13, and is configured to rotate with therotary table 2. Therefore, the rotation shaft 26 and the strut 41 arearranged to penetrate the shield ring 44. The shield ring 44 serves as aheat shielding member for preventing the rotation driving part 27 frombeing exposed to each gas and from being excessively heated.

As shown in FIG. 1, a lower side wall portion 45 which is formed in aconcave shape when seen in a cross-sectional view and surrounds thesupport ring 42, the rotation driving part 27 for the wafer rotation,and the shield ring 44, is formed in a ring shape along the rotationaldirection of the rotary table 2 on the lower side of the chamber body13. Further, five charging mechanisms 46 (only one charging mechanism 46is shown in FIG. 1) are arranged on the bottom portion of the lower sidewall portion 45 while being separated in the circumferential direction.When the processing is not performed on the wafer W, the rotary table 2stops such that the rotation driving part 27 is located right above thecharging mechanism 46, and each of the rotation driving parts 27 ischarged by the charging mechanism 46 in a manner of a non-contact powersupply. Each of the charging mechanisms 46 is arranged by consideringsuch a function. A gas supply path 47 is provided in a space surroundedby the lower side wall portion 45. A gas nozzle 48 is provided to supplyan N₂ gas, for example, while the wafer W is being processed, into thespace surrounded by the lower side wall portion 45 through the gassupply path 47, to purge the space. Although not shown in FIG. 1, forexample, the space is connected to an evacuation path for connecting theevacuation ports 35 and 36 with the evacuation mechanism (not shown), aswill be described later by raising an example, and hence even when aparticle is generated in the space, the particle is purged and removedto the evacuation path by the N₂ gas.

A transfer port 39 for transferring the wafer W and a gate valve 38 foropening/closing the transfer port 39 are provided in a side wall of thechamber body 13 (see FIG. 2), and a delivery of the wafer W is performedbetween a transfer device introduced into the vacuum chamber 11 throughthe transfer port 39 and the recess portion 25. Specifically, throughholes are formed at respective positions of the bottom surface of therecess portion 25, the bottom portion of the chamber body 13, and therotary table 2, and leading ends of pins are configured to move up anddown through each through hole between the space above the recessportion 25 and the lower side of the chamber body 13. The delivery ofthe wafer W is performed by the pin. The pin and each through holethrough which the pin penetrates are omitted in the drawings.

Further, as shown in FIG. 2, a source gas nozzle 51, a separation gasnozzle 52, an oxidizing gas nozzle 53, a plasma generation gas nozzle54, and a separation gas nozzle 55 are arranged at intervals over therotary table 2 in this order in the rotational direction of the rotarytable 2. Each of the gas nozzles 51 to 55 is formed in a rod shapeextending horizontally along the radial direction of the rotary table 2from the side wall toward the center portion of the vacuum chamber 11,and discharges a corresponding gas in a downward direction from aplurality of discharge holes 56 formed along the radial direction.

The source gas nozzle 51 constituting a processing gas supply mechanismdischarges the BTBAS (Bis(tertiary-butyl-amino) silane) gas. A nozzlecover 57 shown in FIG. 2 covers the source gas nozzle 51, which isformed in a fan shape extending toward upstream side and downstream sideof the rotational direction of the rotary table 2. The nozzle cover 57serves to improve adsorption of the BTBAS gas onto the wafer W byincreasing the concentration of the BTBAS gas on a lower side of thenozzle cover 57. The oxidizing gas nozzle 53 discharges an ozone gas.The separation gas nozzles 52 and 55 are gas nozzles for discharging anN₂ gas, and each is arranged to divide the fan-shaped protrusion 17 ofthe ceiling plate 12 in a circumferential direction.

The plasma generation gas nozzle 54 discharges a plasma generation gasincluding a mixed gas of, for example, an argon (Ar) gas and an oxygen(O₂) gas. An opening portion having a fan shape extending in therotational direction of the rotary table 2 is formed through the ceilingplate 12, and a plasma forming part 61 having a cup shape correspondingto a shape of the opening portion and made of a dielectric material suchas quartz is provided to block the opening portion. The plasma formingpart 61 is arranged between the oxidizing gas nozzle 53 and theprotrusion 17 in the rotational direction of the rotary table 2. In FIG.2, a position where the plasma forming part 61 is arranged is shown in adotted and dashed line.

A protruding portion 62 is formed on a bottom surface of the plasmaforming part 61 along a peripheral portion of the plasma forming part61, and a leading end portion of the plasma generation gas nozzle 54penetrates the protruding portion 62 from an outer circumferential sideof the rotary table 2 in order to allow the gas to be discharged in anarea surrounded by the protruding portion 62. The protruding portion 62serves to suppress a decrease of the concentration of the plasmageneration gas by preventing the N₂ gas, the ozone gas, and the BTBASgas from entering into the lower side of the plasma forming part 61.

A recess portion is formed in an upper side of the plasma forming part61, and a Faraday shield 63 having a box shape opened upwards isarranged in the recess portion. An antenna 65 including a metal wirewound in a coil shape around a vertical axis is provided on a bottomsurface of the Faraday shield 63 via an insulating plate member 64, anda radio frequency (RF) power source 66 is connected to the antenna 65. Aslit 67 is formed on the bottom surface of the Faraday shield 63, forpreventing an electric field component of an electromagnetic fieldgenerated from the antenna 65 when applying an RF power to the antenna65 from being directed downwards while causing a magnetic fieldcomponent to be directed downwards. The slit 67 extends in a directionperpendicular to (intersecting with) a winding direction of the antenna65, and a plurality of slits 67 is formed along the winding direction ofthe antenna 65. With this configuration, when the RF power source 66 isturned on and the RF power is applied to the antenna 65, plasma isgenerated from the plasma generation gas supplied to the lower side ofthe plasma forming part 61.

Above the rotary table 2, an area below the nozzle cover 57 of thesource gas nozzle 51 is defined as an adsorption area R1 where anadsorption of the BTBAS gas which is a source gas is performed, and anarea below the oxidizing gas nozzle 53 is defined as an oxidizing areaR2 where an oxidation of the BTBAS gas by the ozone gas is performed.Further, an area below the plasma forming part 61 is defined as a plasmaforming area R3 where a modification of the SiO₂ film is performed byplasma. Areas below the protrusions 17 respectively define separationareas D for preventing the source gas and the oxidizing gas from beingmixed by separating the adsorption area R1 and the oxidizing area R2from each other by the N₂ gas discharged from the separation gas nozzles52 and 55.

The evacuation port 35 is opened at a radially outward position betweenthe adsorption area R1 and the separation area D near the downstreamside of the adsorption area R1 in the rotational direction, and asurplus BTBAS gas is exhausted through the evacuation port 35. Theevacuation port 36 is opened at a radially outward position near aboundary between the plasma forming area R3 and the separation area Dnear the downstream side of the plasma forming area R3 in the rotationaldirection, and a surplus O₃ gas and plasma generation gas are exhaustedthrough the evacuation port 36. The N₂ gases supplied from of theseparation area D, the gas supply pipe 15 on the lower side of therotary table 2, and the center area forming portion C are also exhaustedthrough the evacuation ports 35 and 36.

The film forming apparatus 1 includes a control part 100 implemented bya computer to perform an operation control of the entire apparatus (seeFIG. 1). A program for executing a film forming process described lateris stored in the control part 100. The program controls an operation ofeach part by sending a control signal to the parts of the film formingapparatus 1. Specifically, a supply amount of the gas from each of thegas nozzles 51 to 56, a temperature of the wafer W by the heater 33,supply amounts of the N₂ gases from the gas supply pipe 15 and thecenter area forming portion C, a rotation speed of the rotary table 2 bythe rotation driving part 22, a rotation speed of the wafer holder 24 bythe rotation driving part 27 for the wafer rotation, and the like arecontrolled based on the control signal. In the program, a group of stepsis prepared such that each process described later can be executed byperforming such a control. The program is installed in the control part100 from a recording medium such as a hard disk, a compact disk, anoptomagnetic disk, a memory card, a flexible disk, or the like.

In the film forming apparatus 1, the process is started with therotation of the rotary table 2 so that the wafer W revolves around thecenter of the rotary table 2. The rotation of the wafer W is performedby the rotation of the wafer holder 24 in parallel with the rotation ofthe rotary table 2. However, the rotation of the rotary table 2 and therotation of the wafer holder 24 are not synchronized with each other.More specifically, the wafer W rotates at a certain rotation speed sothat, when the rotary table 2 makes one rotation from a predeterminedposition in the vacuum chamber 11 in which the wafer W is positioned ina first orientation and stops at the predetermined position again, thewafer W can be positioned in a second orientation different from thefirst orientation. The rotation speed A (unit: rpm) of the wafer W isset by the control part 100 based on a parameter inputted by anoperator.

The control part 100 is further described with reference to FIG. 6,which is a block diagram of the control part 100. The control part 100includes a setting part 101 that includes an operation panel with abutton and the like for the operator to input and set the parameter, amemory 102 that stores therein a plurality of processing recipes, and amemory 103 that stores therein a cycle rate R (unit: nm/cycle). Theprocessing recipe is data including, for example, a target filmthickness T (unit: nm) of a SiO₂ film to be formed on the wafer W, aflow rate of a gas supplied from each part of the film forming apparatus1, and a rotation speed V (unit: rpm) of the rotary table 2, whereinthree components are associated with one another. The cycle rate R is anincrease amount of the film thickness obtained when one ALD cycleincluding a supply of the source gas, a supply of the oxidizing gas, anda modification of the film by the plasma is completed. That is, it isequivalent to an increase amount of the film thickness per rotation ofthe rotary table 2.

The control part 100 further includes a work memory 104 and a displaypart 105. Various parameters are input to the work memory 104 from thememories 102 and 103, and a calculation of the rotation speed of thewafer holder 24 is performed based on the parameters. A result of thecalculation in the work memory 104 is displayed on the display part 105.

When the operator performs a predetermined operation on the setting part101, one of the plurality of processing recipes is selected, and thetarget film thickness T and the rotation speed V of the rotary table 2included in the selected processing recipe are loaded in the work memory104 from the memory 102. Further, when the operator performs apredetermined operation on the setting part 101, the cycle rate R isloaded in the work memory 104 from the memory 103.

In the work memory 104, the number of rotations (T/R=M) of the rotarytable 2 from the start of a film forming process to the end of the filmforming process is calculated from the loaded target film thickness Tand cycle rate R. At the time when the film forming process is started,both the rotation of the rotary table 2 and the supply of the gas fromthe source gas nozzle 51 are performed. At the time when the filmforming process ends, at least one of the rotation of the rotary table 2or the supply of the gas from the source gas nozzle 51 is stopped. Thecalculated number of rotations M of the rotary table 2 is displayed onthe display part 105. The operator sets the number of rotations N (N isnatural number) of the wafer holder 24 on the setting part 101 based onthe displayed number of rotations M of the rotary table 2. The number ofrotations N is the number of rotations of the wafer holder 24 from thestart of the film forming process to the end of the film formingprocess.

As the number of rotations N, a numerical value different from a integermultiple of the number of rotations M of the rotary table 2 is set. Thisis for preventing a synchronization between the rotation of the rotarytable 2 and the rotation of the wafer W. In some embodiments, N is aninteger equal to or larger than one. This is because, although the waferW passes through the source gas adsorption area R1 in variousorientations by its rotation and revolution, it is important to increasethe uniformity in the distribution of the film thickness along thecircumferential direction of the wafer W by substantially equalizing thenumber of passes in each orientation.

When the number of rotations N is set, the rotation speed A of the waferW is calculated from the number of rotations N, the rotation speed V ofthe rotary table 2, and the number of rotations of the rotary table 2.Specifically, a formula (the rotation speed A (rpm) of the wafer W=therotation speed V (rpm) of the rotary table×1/M (times)×N) is calculated.The result of the calculation is displayed on the a screen (displaypart) 105. When the calculation of the rotation speed A is completed, itis determined whether or not the rotation speed of the wafer W is equalto or slower than a reference speed, e.g., 10 rpm. When it is determinedthat the rotation speed of the wafer W is equal to or slower than thereference speed, a message saying that the process is ready is displayedon the screen 105, and the operator can start the film forming processby performing a predetermined operation on the setting part 101. On theother hand, when it is determined that the rotation speed of the wafer Wexceeds the reference speed, for example, a message saying that are-setting of each parameter is required is displayed on the screen 105.

When the rotation speed A of the wafer W is high, the orientation of thewafer W during passing through the adsorption area R1 is largelychanged, whereby improved uniformity in the distribution of the filmthickness along the circumferential direction of the wafer W can beobtained regardless of the distribution of the source gas in theadsorption area R1. However, if the rotation speed A of the wafer W istoo fast, the wafer W may be upwardly separated from the wafer holder 24due to a centrifugal force and is likely to be deviated from the waferholder 24. For this reason, in some embodiments, the rotation speed A ofthe wafer W is limited to be equal to or slower than the referencespeed.

The calculation of the rotation speed A (rpm) of the wafer W is furtherdescribed with a specific example. It is assumed that, for example, thetarget film thickness T and the rotation speed V of the rotary table 2are 32 nm and 60 rpm, respectively, and the cycle rate R is 0.095nm/cycle in the selected processing recipe. In the work memory 104, thenumber of rotations M of the rotary table 2 is calculated to be T/R=32(nm)/0.095 (nm/cycle) 337 rotations. When the number of rotations N ofthe wafer W is set, the rotation speed A (rpm) of the wafer W iscalculated to be V (rpm)×1/M (rotations)×N=60×1/337×N≈0.178 rpm. Sincethe number of rotations M of the rotary table 2 is 337, a natural numberother than 337 is set as the number of rotations N in order to preventthe synchronization described above. The above calculation anddetermination are performed by the program of the control part 100.

A film forming process on the wafer W by the film forming apparatus 1 isdescribed below. As described with reference to FIG. 6, when theprocessing recipe is selected and the target film thickness T and therotation speed of the rotary table 2 are set, the reading of the cyclerate R and the setting of the number of rotations N are performed andthe rotation speed of the wafer W is set. The wafer W is then loaded oneach wafer holder 24 by a transfer device (not shown) (see FIG. 7). Afurther description is given by appropriately referring to FIGS. 7 to 10in which the wafer W loaded on the rotary table 2 is schematicallyshown. In FIGS. 7 to 10, each wafer W is represented by W1 to W5 for thesake of convenience. Further, in order to indicate an orientation of thewafer W that is changed during the film forming process, diameters ofthe wafers W1 to W5 that have not subjected to the film forming processare respectively represented by arrows A1 to A5 directed to the centerof the rotary table 2 in an area corresponding to the diameter of therotary table 2.

The gate valve 38 is closed after loading the wafers W1 to W5, theevacuation is performed through the evacuation ports 35 and 36 to causethe inside of the vacuum chamber 11 to be in a vacuum atmosphere of apredetermined pressure, and the N₂ gas is supplied to the rotary table 2from the separation gas nozzles 52 and 55. Further, the N₂ gases as apurge gas are supplied from the center area forming portion C of therotary table 2 and the gas supply pipe 15 at the lower side of therotary table 2, and flow from the center portion of the rotary table 2toward the peripheral portion of the rotary table 2. The temperature ofthe heater 33 rises and the rotary table 2 and the wafer holder 24 areheated by a radiant heat from the heater 33. Further, each of the wafersW1 to W5 is heated to a predetermined temperature by a heat transferfrom the wafer holder 24.

Thereafter, both the rotation of the rotary table 2 at the rotationspeed V set by the operator and the rotation of the wafer holder 24 atthe calculated rotation speed A of the wafer W are started. That is, therevolution and the rotation of the wafer W are started. For example,with the start of the revolution and the rotation, the supply of the gasfrom each of the source gas nozzle 51, the oxidizing gas nozzle 53, andthe plasma generation gas nozzle 54, and the generation of the plasma bythe application of the RF power to the antenna 65 from the RF powersource 66 are started. Each of the gases is supplied at the flow ratespecified in the selected processing recipe. FIG. 8 illustrates a statein which a predetermined time elapses since the film forming process isstarted, the rotary table 2 is rotated 180 degrees from the start of thefilm forming process, and the orientation of the wafer W is changed bythe rotation.

The flow of each of the gases in the vacuum chamber 11 is indicated byan arrow in FIG. 11. Since the separation area D into which the N₂ gasis supplied is formed between the adsorption area R1 and the oxidizingarea R2, the source gas supplied to the adsorption area R1 and theoxidizing gas supplied to the oxidizing area R2 are not mixed over therotary table 2 and are evacuated with the N₂ gas through the evacuationport 35. Further, as the separation area D into which the N₂ gas issupplied is formed between the adsorption area R1 and the plasma formingarea R3, the source gas, the plasma generation gas supplied to theplasma forming area R3, and the oxidizing gas heading for the separationarea D from the upstream side of the plasma forming area R3 in therotational direction are not mixed over the rotary table 2 and areevacuated with the N₂ gas from the evacuation port 36. The N₂ gassupplied from the center area forming portion C and the gas supply pipe15 are also removed from the evacuation ports 35 and 36.

In a state in which the supply and the evacuation of each of the gasesare performed in the above manner, the wafer W1 to W5 sequentially andrepeatedly travels the adsorption area R1 below the nozzle cover 57 ofthe source gas nozzle 51, the oxidizing area R2 below the oxidizing gasnozzle 53, and the plasma forming area R3 below the plasma forming part61 in this order. The BTBAS gas discharged from the source gas nozzle 51is adsorbed on the wafer W in the adsorption area R1, and the adsorbedBTBAS gas is oxidized by the O₃ gas supplied from the oxidizing gasnozzle 53 in the oxidizing area R2, thus forming one or a plurality ofmolecular layers of silicon oxide. In the plasma forming area R3, thesilicon oxide molecular layer is exposed to the plasma and modified.

In the above manner, the wafer holder 24 rotates without beingsynchronized with the rotation of the rotary table 2, and hence each ofthe wafers W1 to W5 is positioned in a different orientation whenever itis located at a predetermined position in the adsorption area R1. FIG. 9illustrates a state in which the rotary table 2 completes one rotationfrom the start of the film forming process. FIG. 10 illustrates a statein which the rotation of the rotary table 2 is continued from the stateshown in FIG. 9 and each of the wafers W1 to W5 shows an orientationrotated 180 degrees from the orientation at the time of starting thefilm forming process. The change of the orientation of each of thewafers W1 to W5 causes each portion of the wafer W in thecircumferential direction to pass a different position in the adsorptionarea R1. Hence, even when a distribution of concentration of the sourcegas at each of the positions in the adsorption area R1 is changed, theamount of source gas adsorbed on the wafer W from the start of the filmforming process to the end of the film forming process can be equalizedon each portion of the wafer W in the circumferential direction.Consequently, the thickness of the SiO₂ film formed on the wafer W canbe suppressed from being unequally distributed on each portion of thewafer W in the circumferential direction.

A continued rotation of the rotary table 2 in the above manner causesthe molecular layer of the silicon oxide to be sequentially laminated,so that a silicon oxide film is formed and its thickness is graduallyincreased. When the film forming process is completed while the targetfilm thickness is obtained, i.e., when the rotary table 2 rotates by thenumber of rotations calculated based on the preset parameters, therotation of the rotary table 2 and the rotation of the wafer holder 24are stopped, and the film forming process is completed. At the time ofending the film forming process, each of the wafers W1 to W5 is locatedat the same position as that at the time of starting the film formingprocess, and since, as described with reference to FIG. 6, the number ofrotations N is set as an integer, each of the wafers W1 to W5 has thesame orientation as that at the time of starting the film formingprocess. Therefore, the wafers W1 to W5 are respectively positioned inorientations shown in FIG. 7. At the time of ending the film formingprocess, the supply of the gasses from the gas nozzles 51 to 55 and thegeneration of the plasma are also stopped. Thereafter, the wafers W1 toW5 are transferred out of the vacuum chamber 11 by the transfer device.

In the film forming apparatus 1, the rotation speed V of the rotarytable 2, the target film thickness T of the SiO₂ film, the cycle rate R,and the number of rotations N of the wafer W are set as the parameter,the rotation speed A of the wafer W is calculated based on the setparameter to allow the wafer W to be positioned in a differentorientation whenever the wafer W is located in the adsorption area R1,and the wafer W rotates at the calculated rotation speed A. Therefore,the uniformity of the film thickness of the SiO₂ film can be improvedalong the circumferential direction of the wafer W.

Further, in the film forming apparatus 1, the operator can freely setthe number of rotations N in the above-described manner. When the numberof rotations N becomes smaller, the change in orientation between thetime when the wafer W is located in the adsorption area R1 and the nexttime the wafer is located in the adsorption area R1 becomes smaller.That is, a dispersion degree between the orientations of the wafer Wwhenever the wafer W is located in the adsorption area R1 becomes largeruntil the end of the film forming process. In other words, the filmforming apparatus 1 has an advantage that the dispersion degree of theorientation can be easily and clearly set. In an example of setting N, Nis set to an integer as described above, whereby the number of times thewafer W passes through the adsorption area R1 is allowed to be uniformfor different orientations, and hence the uniformity of the filmthickness in the circumferential direction can be improved moredefinitely. It is preferred that an integer is set as the number ofrotations N of the wafer W. However, a number equal to or larger thanone including a decimal may be set as the number of rotations N of thewafer W because an unequal distribution of the film thickness in thecircumferential direction can be mitigated even in a case where a numberincluding a decimal is set as the number of rotations N.

In addition, the film forming apparatus 1 is configured such that therotation shaft 26 for supporting the wafer holder 24 is supported by thesupport ring 42 that is supported by the rotary table 2 via the strut41, and the heater 33 is arranged on each of the inner side and theouter side of a traveling path of the strut 41 and the rotation shaft 26traveling with the rotation of the rotary table 2. With thisconfiguration, the wafer W can be heated through the rotary table 2while the heater 33 does not interrupt the traveling of the strut 41 andthe rotation shaft 26.

In the above-mentioned example, it is configured that the rotation speedV of the rotary table 2, the target film thickness T of the SiO₂ film,and the cycle rate R are loaded from the memories 102 and 103 to thework memory 104. However, in some embodiments, at least one of theseparameters may be inputted by an operator from the setting part 101 tothe work memory 104 for the calculation of the rotation speed A of thewafer W.

In one of the example configurations, an operator may set, from thesetting part 101, the rotation speed V of the rotary table 2 and acoefficient K for determining the rotation speed A by being multipliedby V, and the rotation speed A of the wafer W is set at the work memory104 from a calculation of A=V×K. As the coefficient K, a numerical valueallowing the rotation of the wafer W not to be synchronized with therevolution of the wafer W is set, and the value is selected among, e.g.,K=0.1, 0.2, 0.3 . . . , 1.1, 1.2, 1.3 . . . , and the like.

On the other hand, as shown in FIG. 12, a height H1 of the side wall ofthe recess portion 25 of the wafer holder 24, i.e., a depth of therecess portion 25, may be formed to be larger than a thickness H2 of thewafer W in the film forming apparatus 1. In this example, H1 is 1.8times of H2, for example, H1 is 1.8 millimeters, and H2 is 1 millimeter.The reason for setting H1 to be 1.8 times H2 is as follows. As shown inFIG. 11, the N₂ gases discharged from the center area forming portion Cand the separation gas nozzles 52 and 55 flow in a horizontal directionacross the frontal surface of the rotary table 2 to be exhausted. InFIG. 12, only the N₂ gas supplied from the center area forming portion Camong the N₂ gases is indicated by an arrow. H1 is larger than H2 asdescribed above, and hence there is a step between a top portion of theside wall of the recess portion 25 and the peripheral portion of the topsurface of the wafer W. The N₂ gas flowing in the horizontal directionover the recess portion 25 from the outside of the adsorption area R1shows a stationary gas flow at the step of the recess portion 25 on theupstream side in the direction in which the N₂ gas flows, so that aportion having a thick film thickness, which will be described later isformed as shown in FIGS. 25 and 26. That is, a gas puddle 71 is formedby the step.

When the recess portion 25 moves to the adsorption area R1 from theoutside of the adsorption area R1, the surface atmosphere of the wafer Wis changed from the N₂ gas to the source gas, so that the concentrationof the source gas is increased on the surface of the wafer W and thesource gas is adsorbed on the wafer W. However, in the portion in whichthe gas puddle 71 of the N₂ gas is formed, the increase of theconcentration of the source gas by the replacement of the N₂ gas withthe source gas is suppressed compared with the other portions, and hencethe adsorption amount of the source gas is relatively small. Since thewafer W rotates about its axis in the above-mentioned manner, the placeson the peripheral portion of the wafer W in which the gas puddle 71 ofthe N₂ gas is formed or a relatively large gas puddle 71 of the N₂ gasis formed are different whenever the wafer W is located in theadsorption area R1. Thus, over the entire circumference of the wafer W,the film thickness on the peripheral portion can be made smaller thanthe film thickness on the center portion of the wafer W. For example,when an etching apparatus having an etching rate at the center portionof the wafer W higher than that at the peripheral portion is used in anetching process after the film formation and when it is attempted toimprove the uniformity of the film thickness between the peripheralportion and the center portion of the wafer W after the etching process,it is effective to form the recess portion 25 having a property ofH1>H2.

FIG. 13 is a longitudinal cross-sectional view of another configurationof the film forming apparatus 1. A difference between the film formingapparatus 1 shown in FIG. 13 and the film forming apparatus 1 shown inFIG. 1 is that, in the film forming apparatus 1 shown in FIG. 13, aspace 72 is formed on the lower side of the concave portion 31 of thechamber body 13 in which the heater 33 is provided along the rotationaldirection of the rotary table 2, and the support ring 42 and therotation driving part 27 for the wafer rotation are arranged in thespace 72. A wall portion 73 is a wall between the concave portion 31 andthe space 72. A space in the concave portion 31 and the space 72 arerespectively connected to a flow path 74 formed on a downstream side ofthe evacuation port 36 via valves V1 and V2 in the chamber body 13, andthe valves V1 and V2 are opened at a proper opening degree during thefilm forming process.

In FIG. 13, a flow of the N₂ gas supplied from the gas supply pipe 15 isindicated by an arrow. A part of the N₂ gas supplied to the centerportion of the rear surface of the rotary table 2 from the gas supplypipe 15 flows to the evacuation port 36 along the rear surface of therotary table 2 to be removed together with each gas flowing from thefrontal surface of the rotary table 2. The other part of the N₂ gasflows into the concave portion 31 and the space 72 through a gap betweenthe rotation shaft 26 and the shield 34 and a gap between the wallportion 73 and the rotation shaft 26, and reaches the flow path 74. Theother part of the N₂ gas is then removed together with each gasintroduced into the evacuation port 36.

In this manner, the inside of the concave portion 31 and the space 72are purged by the N₂ gas supplied from the gas supply pipe 15. Thisenables a particle generated from the rotation driving part 27 in thespace 72 to be removed from the flow path 74, whereby a scattering ofthe particle to a surrounding portion is more definitely suppressed. Inaddition, it is possible to prevent the heater 33 from deteriorating dueto an adhesion of the source gas and the oxidizing gas to the heater 33.A supply pipe for supplying an N₂ gas to the concave portion 31 and thespace 72 may be provided separately from the gas supply pipe 15.

In the above-described example, the source gas nozzle 51 supplies thesource gas for the ALD method. However, the source gas nozzle 51 maysupply a film forming gas for a film formation by a chemical vapordeposition (CVD) method, so that an orientation of the wafer W ischanged by the rotation of the wafer W around its axis whenever thewafer W is located in an area into which the film forming gas issupplied. That is, the apparatus can be configured without the oxidizinggas nozzle and the separation gas nozzle.

FIG. 14 is a longitudinal cross-sectional view of a film formingapparatus 8 as another example of a film forming apparatus, and FIG. 15is a perspective view of a rotary table 2 of the film forming apparatus8. The film forming apparatus 8 is described below focusing on adifference between the film forming apparatus 8 and the film formingapparatus 1. The rotation shaft 26 of a wafer holder 24 on the rotarytable 2 of the film forming apparatus 8 is arranged to penetrate asupport ring 42 and a magnetic sealing part 20 in a vertical direction.A magnetic gear 81, which is a first rotating member having a horizontaldisk plate shape, is coupled to a bottom portion of the rotation shaft26 in a space 72 described with reference to FIG. 13. The magnetic gear81 includes a plurality of magnets arranged along a circumferentialdirection which is a rotational direction thereof, and the magnets arearranged such that N poles and S poles are located in an alternatemanner along the circumferential direction. The rotation shaft 26rotates around its axis by a rotation of the magnetic gear 81.

Further, a magnetic gear 82, which is a second rotating member having ahorizontal disk plate shape, is provided on a lower side of the magneticgear 81 in the space 72. Like the magnetic gear 81, the magnetic gear 82includes a plurality of magnets. However, the size and the number ofpoles of the magnetic gear 82 differ from those of the magnetic gear 81.A center of the magnetic gear 82 is deviated from a center of themagnetic gear 81 toward a peripheral end of the rotary table 2, in orderto rotate the magnetic gear 81 by the magnetic gear 82, as describedlater. The magnetic gear 82 is coupled to a rotation driving part 84provided on a bottom portion of the film forming apparatus 8 via arotation shaft 83. The rotation driving part 84 rotates the magneticgear 82 via the rotation shaft 83.

The rotation driving part 84 includes a magnetic sealing part 85 and amotor (not shown). The magnetic sealing part 85 includes a bearing forthe rotation shaft 83 and a magnetic seal for sealing a gap around therotation shaft 83, and is configured to suppress a scattering of aparticle generated from the bearing to the space 72 of a vacuumatmosphere. Specifically, for example, the magnetic sealing part 85prevents a scattering of a lubricant used in the bearing to the space72. Further, the magnetic sealing part 85 also serves to partition thevacuum atmosphere of the space 72 from the atmospheric environmentoutside the vacuum chamber 11. In the film forming apparatus 8, asdescribed with reference to FIG. 13, the N₂ gas is flown into theconcave portion 31 and the space 72 from a gas supply pipe 15, therebypurging the concave portion 31 and the space 72. Further, like the filmforming apparatus 1, a gas supply path 47 for supplying the N₂ gas froma gas nozzle 48 is opened into the space 72, thereby purging the space72 by the N₂ gas.

The magnetic gear 81 revolves by a revolution of the wafer holder 24,and passes above the rotating magnetic gear 82 such that a peripheralportion of the magnetic gear 81 and a peripheral portion of the magneticgear 82 are overlapped with each other. While the peripheral portion ofthe magnetic gear 81 and the peripheral portion of the magnetic gear 82are overlapped with each other, the magnetic gear 81 rotates in anon-contact manner with respect to the magnetic gear 82 at a number ofrotations corresponding to that of the magnetic gear 82 by a magneticforce exerted between the magnetic gear 81 and the magnetic gear 82. Therotation of the magnetic gear 81 causes the wafer holder 24 to rotate,and consequently, the wafer W rotates. That is, in the film formingapparatus 8, the rotation of the wafer W is only performed in a limitedtime for which the magnetic gear 81 and the magnetic gear 82 areoverlapped with each other, and hence the rotation of the wafer W isperformed intermittently during the revolution thereof. In this example,the size and the number of poles are set such that a rotation speed ofthe magnetic gear 81 becomes slower than that of the magnetic gear 82.

As in the film forming apparatus 1, the operator selects a recipe (thetarget film thickness T and the rotation speed V of the rotary table 2),the cycle rate R, and the number of rotations N from a setting part 101in the film forming apparatus 8, so that the rotation speed A (rpm) ofthe wafer W is calculated. The number of rotations of the motor thatconstitutes the rotation driving part 84 rotating the magnetic gear 82is then controlled such that the wafer W is allowed to rotate at thecalculated rotation speed.

FIGS. 16 to 18 are schematic diagrams illustrating the rotation andrevolution of the wafer W during a film forming process. In FIGS. 16 to18, as in FIGS. 7 to 10, the wafers W are represented by W1 to W5,respectively, and orientations of the wafers W1 to W5 are represented byarrows A1 to A5, respectively. At the time of a film forming process,each gas is supplied in the same manner as in the film forming apparatus1. The rotary table 2 rotates at the rotation speed set by the operator,and the wafer W revolves by the rotation of the rotary table 2. Whilethe wafer revolves, the motor of the rotation driving part 84 rotates atthe rotation speed calculated in the above manner based on the rotationspeed of the rotary table 2, thereby rotating the magnetic gear 82 (seeFIG. 16).

For example, when the magnetic gear 81 coupled to the wafer holder 24holding the wafer W1 is moved to above the magnetic gear 82 from anupstream side of the rotational direction by the rotation of the rotarytable 2 to be overlapped with the magnetic gear 82, the rotation of themagnetic gear 81 is started by the magnetic force between the magneticgear 81 and the magnetic gear 82, thereby rotating the wafer W1 (seeFIG. 17). When the rotation of the rotary table 2 continues and themagnetic gear 81 is moved to a downstream side of the rotationaldirection with respect to the magnetic gear 82, the magnetic force isweakened and the rotation of the wafer W1 is stopped. As describedabove, since the rotation speed of the wafer W is calculated based onthe rotation speed of the rotary table 2, the orientation of the waferW1 when it stops its rotation differs from the orientation when itstarts the rotation, and in the state in which the orientation ischanged, the wafer W1 moves to the adsorption area R1 by the revolution.A change amount of the orientation depends on the rotation speed of thewafer W calculated in the above manner.

While the revolution continues, whenever the magnetic gear 81 moves to aposition above the magnetic gear 82, the wafer W1 rotates and has achanged orientation in the above-described manner, so that the wafer W1enters into the adsorption area R1 with the changed orientation. In thesame manner as the wafer W1, the wafers W2 to W5 enter into theadsorption area R1 with orientations changed by the rotation in everyrevolution. Therefore, in the same manner as the film forming apparatus1, the film forming apparatus 8 can improve the uniformity of the filmthickness along the circumferential direction of the wafer W. Inaddition, as the film forming apparatus 8 does not necessitate aplurality of rotation driving parts 84 to rotate the wafers W1 to W5,respectively, a cost for manufacturing the apparatus can be decreased.Further, as the magnetic gears 81 and 82 are coupled with each other ina non-contact manner to transfer the power of the rotation driving part84 to the wafer holder 24, the generation of the particle is suppressed.Even when a particle is generated between the rotation shaft 26 forrotating the wafer W and the support ring 42 for supporting the rotationshaft 26, the particle is prevented from being attached on the wafer Wsince the rotation shaft 26 and the support ring 42 are arranged in thespace 72 that is purged by the N₂ gas at the time of the film formingprocess.

Although the film forming apparatus 8 includes only one set of themagnetic gear 82 and the rotation driving part 84, a plurality of setsof the magnetic gear 82 and the rotation driving part 84 may be providedso that the wafers W at a plurality of locations rotate while the waferW makes one revolution. Further, the magnetic gears 81 and 82 may bearranged in parallel with each other in a horizontal direction as shownin FIG. 19, so that the magnetic gear 81 located near the magnetic gear82 by the revolution is selectively rotated, thereby rotating the waferW intermittently. Although the magnetic gears 81 and 82 are shown in acircular columnar shape in the example shown in FIG. 19, these magneticgears include a plurality of magnets, like the magnetic gears 81 and 82having the a disk plate shape shown in FIGS. 14 and 15. Although boththe magnetic gears 81 and 82 include the magnets in the above example,one of them may be implemented by a magnetic body instead of the magnet.For example, the magnetic gear 82 may be formed of a magnet, and themagnetic gear 81 may be formed of a magnetic body such as iron.Accordingly, as described in a previous example, when the magnetic gear81 approaches the magnetic gear 82, the magnetic gear 81 is rotated inresponse to the rotation of the magnetic gear 82, thereby rotating thewafer W. In some embodiments, the magnetic gear 81 may include amagnetic body while the magnetic gear 82 including a magnet.

(Evaluation Test)

An evaluation test of the film forming apparatus according to thepresent disclosure is described below. In the description of eachevaluation test, for the wafer W loaded on the wafer holder 24, the linepassing through the center of the wafer W, which matches the linepassing through the center of the rotary table 2 at the time of startingthe film forming process, is referred to as a Y line. Therefore, the Yline corresponds to a line represented by each of the arrows A1 to A5shown in FIG. 7. The line of the wafer W perpendicular to the Y line isreferred to as an X line.

Evaluation Test 1

A test was performed to investigate a change of distribution of the filmthickness due to the rotation of a wafer W having a diameter of 300 mm.As an evaluation test 1-1, a simulation was performed, in which a filmwas formed on the wafer W without rotating the wafer W in the filmforming apparatus 1. Further, as an evaluation test 1-2, a simulationwas performed, in which a film was formed on the wafer W under the samecondition as that in the evaluation test 1-1 except that the rotation ofthe wafer W was performed. In the evaluation test 1-2, unlike theembodiments, the wafer was set to rotate only by 180 degrees from thestart of the film forming process until the end of the film formingprocess. Moreover, as an evaluation test 1-3, the same evaluation testas the evaluation test 1-2 was performed except that the wafer W was setto rotate only 45 degrees. In addition, as an evaluation test 1-4, asimulation was performed under the same condition as those of theevaluation tests 1-1 to 1-3, except that the wafer W was set to rotateon its axis for a integer number as in the embodiments. In each of theevaluation tests 1-1 to 1-4, the distribution of the in-plane filmthickness on the wafer W was measured.

FIGS. 20A and 20B illustrate the distributions of the in-plane filmthickness on the wafer W in the evaluation tests 1-1 and 1-2,respectively, and FIGS. 21A and 21B illustrate the distributions of thein-plane film thickness on the wafer W in the evaluation tests 1-3 and1-4, respectively. An actual test result is a computer graphic in whichcolors are allocated depending on the in-plane film thickness on thewafer W. However, FIGS. 20A through 21B show shapes formed by encirclingareas in the wafer plane having the same predetermined thickness rangeas a contour line, for the sake of convenience.

FIG. 22A is a graph showing the distribution of the film thickness onthe Y line in the evaluation tests 1-1 and 1-4, and FIG. 22B is a graphshowing the distribution of the film thickness on the X line in theevaluation tests 1-1 and 1-4. The horizontal axis of each of the graphsrepresents a distance (unit: millimeter) from an end of the wafer W. Theend of the wafer W in the graph of the Y line refers to an end on thecenter shaft side of the rotary table 2. The vertical axis of each graphrepresents a film thickness (unit: nanometer). FIG. 23A is a graphshowing the distribution of the film thickness on the Y line in theevaluation tests 1-2 and 1-3, and FIG. 23B is a graph showing thedistribution of the film thickness on the X line in the evaluation tests1-2 and 1-3.

From the schematic diagrams of the wafer W in FIGS. 20A through 21B, itis found that the uniformity of the film thickness along thecircumferential direction of the wafer W was improved by rotating thewafer W, and that the uniformity of the film thickness along thecircumferential direction was considerably improved in the evaluationtests 1-4 in which the wafer W was rotated for the integer number.Further, from each of the graphs, it is found that the distribution ofthe film thickness on the X line did not show a big difference betweenthe evaluation tests 1-1 to 1-4. Regarding the distribution of the filmthickness on the Y line, a slight difference in the film thicknessbetween one end portion and the other end portion of the Y lineappearing in the evaluation test 1-1 is decreased in the evaluationtests 1-2 and 1-3 and substantially disappeared in the evaluation test1-4. That is, it is also found from each of the graphs that theuniformity of the distribution of the film thickness in thecircumferential direction of the wafer W has been improved.

For the evaluation tests 1-1 to 1-4, Table 1 shows an average value ofthe film thickness, the maximum film thickness, the minimum filmthickness, a difference between the maximum film thickness and theminimum film thickness, and WinW that is an index indicating thein-plane uniformity, all of which are calculated from film thicknessesmeasured at 49 points on the wafer plane including each measurementpoint on the X line and Y line. The WinW is represented by ±{(maximumfilm thickness−minimum film thickness)/(average value of filmthickness)}/2×100(%), and Table 1 shows an absolute value of the WinW.The smaller this absolute value is, the higher the in-plane uniformityis. Comparing the WinW values of the evaluation tests 1-1 to 1-4, it isfound that the uniformity of the film thickness has been improved notonly in the circumferential direction of the wafer W but also on theentire plane of the wafer W by rotating the wafer W, and that theevaluation test 1-4 shows the highest uniformity of the film thicknesson the entire plane of the wafer W among the four evaluation tests.Accordingly, from the evaluation test 1, it is found that the rotationof the wafer W is effective in improving the uniformity of the filmthickness as described in the above-mentioned embodiments and thatsetting an integer as the number of rotations is particularly effectivein achieving the uniformity of the film thickness.

TABLE 1 Maximum Average Maximum Minimum value − value value valueMinimum (nm) (nm) (nm) value (nm) WinW Evaluation 32.19 32.42 31.77 0.651.01 test 1-1 Evaluation 32.19 32.34 32.06 0.28 0.44 test 1-2 Evaluation32.19 32.23 32.18 0.05 0.08 test 1-3 Evaluation 32.19 32.23 32.19 0.050.07 test 1-4

Evaluation Test 2

As an evaluation test 2, a test was performed to investigate aninfluence of the height H1 of the side wall of the recess portion 25 ofthe wafer holder 24 described with reference to FIG. 12 and the rotationof the wafer W on the distribution of the film thickness. In anevaluation test 2-1, a simulation in which a film forming process wasperformed without rotating the wafer W in the film forming apparatus 1,as in the evaluation test 1-1, was performed under the condition wherethe height H1 of the side wall is set to be 1.0 millimeter that is thethickness H2 of the wafer W. The number of rotations of the rotary table2 was set to be 120 rpm. Further, as an evaluation test 2-2, asimulation was performed under the same conditions as those in theevaluation test 2-1 except that the wafer W rotated and revolved, andthe thickness of the film was measured at each portion of the wafer W.Moreover, as evaluation tests 2-3 and 2-4, a simulation was performedunder the same condition as those in the evaluation tests 2-1 and 2-2,respectively, except that the height H1 of the side wall was set to be1.8 millimeters as shown in FIG. 12. The film thickness on each portionof the wafer W was measured for the evaluation tests 2-1 to 2-4.

FIGS. 24A and 24B schematically show images of the distribution of thefilm thickness on the wafer W obtained in the evaluation tests 2-1 and2-2, respectively, in the same manner as in the evaluation test 1. FIGS.25A and 25B schematically show wafers related to the evaluation tests2-3 and 2-4, respectively, in the same manner as FIGS. 24A and 24B. FIG.26A shows a graph of the distribution of the film thickness on the Xline in the evaluation tests 2-1 and 2-2, and FIG. 26B shows a graph ofthe distribution of the film thickness on the Y line in the evaluationtests 2-1 and 2-2. FIG. 27A shows the distribution of the film thicknessof the X line in the evaluation tests 2-3 and 2-4, and FIG. 27B shows agraph of the distribution of the film thickness of the Y line in theevaluation tests 2-3 and 2-4. The horizontal axis of each of the graphsshown in FIGS. 26A to 27B represents a distance from an end of the waferW, like the horizontal axis of each of the graphs in the evaluationtest 1. However, the vertical axis represents a deposition rate (unit:nm/min) instead of the film thickness.

From the schematic diagrams and the graphs of FIGS. 24A to 27B, it isfound that the uniformity of the film thickness in the circumferentialdirection of the wafer W can be improved by rotating the wafer Wregardless of the height H1 of the side wall. Regarding the filmthickness at both end portions of the X line and the Y line, it wasfound that the film thickness was about 5.5 millimeters in theevaluation test 2-2 in which the height H1 of the side wall is set to be1 millimeter, and the evaluation test 2-4 in which the height H1 of theside wall is set to be 1.8 millimeters shows about 5.0 millimeters,i.e., the evaluation test 2-4 obtains a thinner film thickness.Therefore, in order to reduce the film thickness on the peripheralportion of the wafer W, it is effective to set the height H1 of the sidewall to be larger than the thickness of the wafer W and to form a stepbetween the recess portion 25 and the wafer W as described in theabove-mentioned embodiments.

In the same manner as the evaluation test 1, for the evaluation tests2-1 to 2-4, Table 2 shows an average value of the film thickness, themaximum value of the film thickness, the minimum value of the filmthickness, a difference between the maximum value and the minimum value,and WinW that is an index indicating the in-plane uniformity, all whichare calculated from film thicknesses measured at measurement points onthe wafer W. From a comparison of the test results of the evaluationtests 2-1 and 2-2 and a comparison of the test results of the evaluationtests 2-3 and 2-4, it is found that the WinW can be decreased byrotating the wafer W. Accordingly, it is found that the uniformity ofthe film thickness can be improved not only in the circumferentialdirection of the wafer W but also on the entire plane of the wafer W byrotating the wafer W.

TABLE 2 Maximum Average Maximum Minimum value − value value valueMinimum (nm) (nm) (nm) value (nm) WinW Evaluation 5.50 6.03 4.91 1.1210.24 test 2-1 Evaluation 5.50 5.58 5.44 0.14 1.31 test 2-2 Evaluation5.07 5.61 4.66 0.96 9.36 test 2-3 Evaluation 5.07 5.10 5.04 0.06 0.63test 2-4

Evaluation Test 3

As an evaluation test 3, an influence of the recess portion 25 of thewafer holder 24 on the distribution of the film thickness wasinvestigated. In the evaluation test 3, a simulation in which a film wasdeposited on the wafer W without rotating the wafer W was performed, andthe film thickness was measured on each portion of the wafer W. Theheight H1 of the side wall of the recess portion 25 was set to be 1.0millimeter in evaluation tests 3-1 to 3-3, and was set to be 1.8millimeters in evaluation tests 3-4 to 3-6. The number of rotations ofthe rotary table 2 was set to be 20 rpm in the evaluation tests 3-1 and3-4, 60 rpm in the evaluation tests 3-2 and 3-5, and 120 rpm in theevaluation tests 3-3 and 3-6. Conditions set for the film formingprocess were the temperature of the wafer W of 600 degrees C., apressure in the vacuum chamber 11 of 1.8 Torr (240.0 Pa), a flow rate ofthe source gas of 200 sccm (0.34 Pa·m³/sec), a flow rate of the O₃ gasas the oxidizing gas of 6 slm (1.01 Pa·m³/sec), a flow rate of the N₂gas from the center area forming portion C of 0 sccm, and a time forperforming the film forming process of 10 min.

FIGS. 28A to 28C schematically show images of the distribution of thefilm thickness on the wafer W obtained in the evaluation tests 3-1, 3-2,and 3-3, respectively, in the same manner as FIGS. 20A to 21B in theevaluation test 1. FIGS. 29A to 29C schematically show images of thedistribution of the film thickness on the wafer W obtained in theevaluation tests 3-1, 3-2, and 3-3, respectively, like FIGS. 28A to 28C.FIGS. 30A and 30B show graphs of the distributions of the film thicknessof the X line and the Y line, respectively, in the evaluation tests 3-2to 3-6. The horizontal axis and the vertical axis of each of the graphsof FIGS. 30A and 30B represent the distance from an end of the wafer Wand the deposition rate, respectively, like the horizontal axis and thevertical axis of each of the graphs of FIGS. 26A to 27B in theevaluation test 2. The distributions of the film thickness of the X lineand the Y line in the evaluation test 3-1 showed substantially the sameresult as those of the evaluation test 3-4, and an indication thereof isomitted from the graph.

From the above graphs and schematic diagrams, it is found that the filmthickness of a part of the peripheral portion of the wafer W was thinnerthan the film thickness of the other area in the evaluation tests 3-5and 3-6 in which the number of rotations of the rotary table 2 isrelatively high and the height H1 of the side wall of the recess portion25 is set to be 1.8 millimeters. It is estimated that, since thedistribution gradient of the film thickness is made even along thecircumferential direction of the wafer W by the rotation of the wafer W,the film thickness of the peripheral portion in the entire circumferenceof the wafer W can be decreased by setting the height H1 of the sidewall of the recess portion in the above-described manner, rotating thewafer W, and setting the number of rotations of the rotary table 2 to berelatively high.

According to the present disclosure, the rotation speed of the substrateis calculated based on the parameter including the rotation speed of therotary table, and then the substrate is rotated at the calculatedrotation speed. This enables the orientation of the substrate to besurely changed whenever the substrate is located in the gas supplyregion over the rotary table. Hence the film can be formed with a highlyuniform thickness in the circumferential direction of the substrate.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A film forming apparatus of forming a thin filmon a substrate by supplying a processing gas to the substrate, the filmforming apparatus comprising: a rotary table disposed in a vacuumchamber and having a loading area formed at a first surface side of therotary table, the rotary table configured to revolve the substrateloaded on the loading area; a rotation mechanism configured to rotatethe loading area such that the substrate rotates around its axis; aprocessing gas supply mechanism configured to supply the processing gasto a processing gas supply area at the first surface side of the rotarytable so that the thin film is formed on the substrate which repeatedlypasses through the processing gas supply area for a plurality of timesby the revolution of the substrate; and a control part configured toperform a calculation of a rotation speed of the substrate based on aparameter including a rotation speed of the rotary table to allow anorientation of the substrate to be changed whenever the substrate ispositioned in the processing gas supply area, and to output a controlsignal for rotating the substrate at a calculated rotation speed.
 2. Thefilm forming apparatus according to claim 1, wherein the calculationincludes a calculation of a product of (i) the rotation speed of therotary table and (ii) a value obtained from a division of an increaseamount of film thickness per rotation of the rotary table by a targetfilm thickness.
 3. The film forming apparatus according to claim 2,wherein the calculation includes a calculation of a product of (i) therotation speed of the rotary table, (ii) the value obtained from thedivision of the increase amount of film thickness per rotation of therotary table by the target film thickness, and (iii) a natural numberequal to or larger than one, and a setting part through which anoperator sets the value of the natural number is provided.
 4. The filmforming apparatus according to claim 1, wherein the rotation mechanismincludes a rotation shaft installed at a second surface side of therotary table and revolving by a rotation of the rotary table, a supportmember is installed at the second surface side of the rotary table inorder to support the rotation shaft against the rotary table, and aheater configured to heat the rotary table from the second surface sideis installed along a rotational direction of the rotary table on aninner side and an outer side of a traveling path of the rotation shaftand the support member.
 5. The film forming apparatus according to claim4, wherein the support member includes: a plurality of struts installedat the second surface side of the rotary table and separated from eachother along a rotational direction of the rotary table with respect tothe rotation shaft, and a coupling part configured to support therotation mechanism against the strut by coupling the strut to therotation mechanism at a lower side of the heater.
 6. The film formingapparatus according to claim 1, further comprising a first rotatingmember configured to revolve together with the loading area andincluding a magnet or a magnetic body which rotates the loading area bya rotation thereof, wherein the rotation mechanism includes a secondrotating member including a magnet or a magnetic body, at least one ofthe first rotating member and the second rotating member includes amagnet, and the first rotating member that revolves is intermittentlyrotated by a magnetic force between the first rotating member and thesecond rotating member in a non-contacting manner.
 7. The film formingapparatus according to claim 1, further comprising: a reaction gassupply mechanism configured to supply a reaction gas that reacts withthe processing gas to a reaction gas supply area formed separately fromthe processing gas area in a circumferential direction of the rotarytable; and a separation gas supply part configured to supply aseparation gas to a separation area between the processing gas supplyarea and the reaction gas supply area, wherein the loading area isdefined by a bottom surface of a recess portion, and a depth of therecess portion is larger than a thickness of the substrate.
 8. The filmforming apparatus according to claim 7, wherein the depth of the recessportion is 1.8 times as large as the thickness of the substrate.
 9. Amethod of forming a thin film on a substrate by supplying a processinggas to the substrate, the method comprising: loading the substrate on aloading area formed at a first surface side of a rotary table disposedin a vacuum chamber and revolving the substrate; rotating the loadingarea by a rotation mechanism to rotate the substrate; supplying theprocessing gas to a processing gas supply area at the first surface sideof the rotary table by a processing gas supply mechanism so that thethin film is formed on the substrate which repeatedly passes through theprocessing gas supply area by a plurality of times; calculating arotation speed of the substrate based on a parameter including arotation speed of the rotary table to allow an orientation of thesubstrate to be changed whenever the substrate is positioned in theprocessing gas supply area, and rotating the substrate at a calculatedrotation speed.
 10. The method according to claim 9, wherein thecalculating includes a calculation of a product of (i) the rotationspeed of the rotary table and (ii) a value obtained from a division ofan increase amount of film thickness per rotation of the rotary table bya target film thickness.
 11. The method according to claim 10, whereinthe calculating includes a calculation of a product of (i) the rotationspeed of the rotary table, (ii) the value obtained from the division ofthe increase amount of film thickness per rotation of the rotary tableby the target film thickness, and (iii) a natural number equal to orlarger than one, and setting the natural number.
 12. The methodaccording to claim 9, wherein the rotating the loading area includesrevolving a first rotating member including a magnet together with theloading area; intermittently rotating the first rotating member in anon-contacting manner by a magnetic force between the first rotatingmember and a second rotating member constituting the rotation mechanismand including a magnet; and rotating the loading area by a rotation ofthe first rotating member.
 13. A non-transitory computer-readablerecording medium storing therein a computer program used in a filmforming apparatus in which a thin film is formed on a substrate bysupplying a processing gas to the substrate, wherein the computerprogram is configured to execute the method according to claim 9.